1. Field of the Invention
The present invention relates to a technology for driving a display panel composed of a set of cells that are display elements having a memory function. More particularly, this invention is concerned with a device for displaying an image on an alternating current (AC) type plasma display panel (PDP) with interlaced scanning.
2. Description of the Related Art
An AC type PDP sustains discharge by applying a voltage waveform alternately to two sustaining electrodes, and glows for display. One discharge completes in one to several microseconds immediately after application of a pulse. Positively charged ions that are derived from the discharge are accumulated on the surface of an insulating layer over electrodes to which a negative voltage is applied. Likewise, electrons carrying negative charges are accumulated on the surface of the insulating layer over electrodes to which a positive voltage is applied.
Discharge is effected with a high-voltage (writing voltage) pulse (writing pulse) in order to generate a wall charge. Thereafter, a pulse (retaining discharge pulse) of a voltage of opposite polarity (retaining discharge voltage), which is lower than the previous voltage, is applied. The accumulated wall charge is added to the voltage. The voltage in a discharge space therefore rises and exceeds the threshold value of a discharge voltage. Eventually, discharge starts. Display cells have the feature that once a display cell is discharged for writing and produces a wall charge, when sustaining discharge pulses of opposite polarities are applied alternately to the display cell, the display cell sustains discharge. This feature is called a memory effect or memory function. In general, the AC type PDP utilizes the memory effect to achieve display.
In an AC type PDP of a prior art, X electrodes that are one set of sustaining electrodes and Y electrodes that are the other set thereof are arranged alternately. Discharge occurs in regions between odd-numbered X electrodes and Y electrodes, and in regions between even-numbered X electrodes and Y electrodes. In other words, display cells are defined between the odd-numbered X electrodes and Y electrodes, and between the even-numbered X electrodes and Y electrodes. No display cell is defined between the odd-numbered Y electrodes and even-numbered X electrodes and between the odd-numbered X electrodes and even-numbered Y electrodes. However, this poses a problem of difficulty in attaining high definition and high luminance. The present applicant has disclosed a PDP for interlaced scanning and a driving method thereof in Japanese Unexamined Patent Publication No. 9-160525. The driving method is called an ALiS method (Alternate Lighting of Surfaces Method) and the PDP of this type is called an ALiS PDP. In the ALiS PDP, display cells are defined even by the odd-numbered Y electrodes and even-numbered X electrodes and by the odd-numbered X electrodes and even-numbered Y electrodes. Thus, high definition and high luminance are ensured. The present invention is adapted to an ALiS plasma display panel (PDP) in which, similarly to the one disclosed in the Japanese Unexamined Patent Publication No. 9-160525, regions defined by a Y electrode and X electrodes across the Y electrode are discharged in order to define display cells.
In the PDP of the prior art, a scan driver is formed with an IC mounted on one chip or ICs mounted on several chips in order to realize a compact design or reduced manufacturing cost. The scan driver is provided with a circuit for generating a scanning pulse as mentioned above. If the scan driver is not formed with an IC, the scan driver as well as the circuit must be composed of discrete parts. A problem arises in terms of circuit scale or cost. Even in the PDP to which the present invention is adapted, a scan driver should preferably be formed with an IC in order to realize a compact design and reduce manufacturing cost. However, a problem underlies the PDP to which the present invention is adapted. Namely, the wiring in a drive circuit for driving the X electrodes or Y electrodes is complex. There is therefore difficulty in forming the scan driver with an IC.
An object of the present invention is to simplify the wiring in a drive circuit for driving X electrodes or Y electrodes in a PDP in which different sustaining discharge signals are applied to odd-numbered and even-numbered X electrodes and Y electrodes respectively, and to permit formation of a scan driver with an IC.
To accomplish the above object, in a plasma display device of the present invention, a scan driver is divided into a circuit connected to odd-numbered Y electrodes and a circuit connected to even-numbered Y electrodes. Owing to this configuration, only one kind of sustaining discharge signal is present in a chip. A problem concerning durability to a high voltage will not occur. The scan driver can be formed with an IC. Moreover, similarly to the drive circuit for driving the Y electrodes, a drive circuit for driving X electrodes is divided into a circuit connected to odd-numbered X electrodes and a circuit connected to even-numbered X electrodes.
To be more specific, the plasma display device of the present invention has a display panel including first and second electrodes arranged in parallel with one another, and third electrodes arranged orthogonally to the first and second electrodes. With a scanning signal and addressing signal to be applied to the second and third electrodes, discharge cells are selected. By applying sustaining discharge signals to the first and second electrodes respectively, the selected cells sustain a discharge. The sustaining discharge signals that are mutually out of phase are applied alternately to a pair of adjoining first electrodes and a pair of adjoining second electrodes. Consequently, first display cells are defined between the second electrodes and the first electrodes on one side of the second electrodes. Second display cells are defined between the second electrodes and the first electrodes on the other side of the second electrodes. Interlacing, where the first display cells and second display cells are allowed to glow alternately and repeatedly, is carried out. A drive circuit for driving the second electrodes in the plasma display device includes a first drive circuit for outputting a pulsating voltage to be applied in common to the odd-numbered ones of the second electrodes, a second drive circuit for outputting a pulsating voltage to be applied in common to the even-numbered ones of the second electrodes, and third circuits associated with the second electrodes for applying the pulsating voltages output from the first drive circuit and second drive circuit to the second electrodes and for applying a scanning signal selectively to the second electrodes. In the plasma display device, the third circuits are grouped into third odd circuits connected to the odd-numbered ones of the second electrodes, and third even circuits connected to the even-numbered ones of the second electrodes. The third odd circuits are integrated into at least one chip and the third even circuits are integrated into at least one chip.
In the plasma display device of the present invention, the drive circuit for driving the second (Y) electrodes is divided into the circuit connected to the odd-numbered Y electrodes and the circuit connected to the even-numbered Y electrodes. This leads to improved freedom in wiring. Moreover, when the third odd circuits and third even circuits are formed with ICs, only one kind of sustaining discharge signal is present within one chip. No problem will therefore occur in relation to durability to a high voltage.
For arranging the foregoing circuits, preferably, the chip having the third odd circuits is located near the first circuit, and the chip having the third odd circuits is located near the second circuit.
For matching the orders of output from the chips having the third odd circuits and third even circuits with the order of arrangement of the Y electrodes, an arrangement changing means is included for modifying a wiring pattern on a circuit board or routing of cables.
When a plurality of first circuits and a plurality of second circuits are included, the first circuits and second circuits should preferably be arranged alternately. Furthermore, when the third odd circuits and third even circuits are each formed with a plurality of chips, the chips should preferably be arranged alternately while being associated with the first circuits and second circuits.
A selection voltage and non-selection voltage, to be used during scanning, are shared by the first and second circuits. A fourth circuit may be included for supplying the voltages.
At least a current supply line and current return line are laid between the first circuit and third odd circuits and between the second circuit and third even circuits.
The fourth circuit includes a first switching element for applying a selection voltage, first and second diodes connected to the first switching element, a second switching element for applying a non-selection voltage, and third and fourth diodes connected to the second switching element. The first diode is connected to one terminal of each of the third odd circuits, and the third diode is connected to the other terminals of the third odd circuits. The second diode is connected to one terminal of each of the third even circuits, and the fourth diode is connected to the other terminals of the third even circuits.
The first and second circuits each include at least a switching element for supplying a sustaining discharge voltage and a switching element for supplying a voltage to be selectively applied to the second electrodes at the time of application of the scanning signal.
The first circuit and the chip having the third odd circuits are mounted on one side of a substrate, and the second circuit and the chip having the third even circuits are mounted on the other side thereof. This leads to simple wiring. Moreover, the chip having the third odd circuits may be mounted on one side of a substrate and the chip having the third even circuits may be mounted on the other side thereof. The first and second circuits may be mounted on one side of the substrate or the other side thereof.
Output terminals on the chip having the third odd circuits and those on the chip having the third even circuits, through which a scanning signal is output sequentially, should preferably be arranged so that the scan signal will be output sequentially in the same direction with respect to one side of the substrate. Thus, the arrangement should preferably be matched with the arrangement of the Y electrodes in the panel.
Moreover, according to another aspect of the present invention, there is provided a plasma display device having a display panel in which first and second electrodes are arranged in parallel with one another, and third electrodes are arranged orthogonally to the first and second electrodes. According to a scanning signal and addressing signal to be applied to the second and third electrodes, a discharge cell is selected. By applying sustaining discharge signals to the first and second electrodes, the selected discharge cell is caused to sustain discharge. In the plasma display device, sustaining discharge signals that are mutually out of phase are applied alternately to the first adjoining electrodes and the second adjoining electrodes. Consequently, first display cells are defined between the second electrodes and the first electrodes on one side of the second electrodes, and second display cells are defined between the second electrodes and the first electrodes on the other side of the second electrodes. Interlacing where the first display cells and second display cells are allowed to glow for display alternately and repeatedly is thus carried out. A drive circuit for driving the first electrodes in the plasma display device includes a fifth drive circuit for outputting a pulsating voltage to be applied in common to the odd-numbered ones of the first electrodes, and a sixth drive circuit for outputting a pulsating voltage to be applied in common to the even-numbered ones of the first electrodes. Pluralities of fifth circuits and sixth circuits are included and arranged alternately.
The fifth and sixth circuits each include at least a switching element for supplying a sustaining discharge voltage and a switching element for supplying a voltage to be applied selectively to the first electrodes at the time of application of the scanning signal.
The fifth circuits are mounted on one side of a substrate, and the sixth circuits are mounted on the other side thereof. This leads to simple wiring.